@article{SF_1988__37_1_134911,
     author = {Peter M. Higgins},
     title = {The range order of a product of i transformations from a finite full transformation semigroup.},
     journal = {Semigroup forum},
     pages = {31--36},
     publisher = {mathdoc},
     volume = {37},
     number = {1},
     year = {1988},
     zbl = {0636.20041},
     url = {http://geodesic.mathdoc.fr/item/SF_1988__37_1_134911/}
}